Insulator



J. J. TAYLOR April 25, 1939.

INSULATOR Filed Nov. 14, 1936 m H AN? 0 R W m mr H J. m J

Patented Apr. 25, 1939 UNITED STATES INSULATOB John J. Taylor,Wadsworth, Ohio, assignor to The Ohio Brass Com corporation oi Ohio my,Mansfield, Ohio, a

Application November 14, 1938, Serial No. 110,885

8 Claims.

This invention relates to electrical insulators, and has for one of itsobjects the provision of an insulator'particularly well adapted for usewhere it is exposed to moisture, such as rain or fog.

A further object of the invention is to provide an insulator in whichmoisture on its surface will form a continuous leakage path ofsubstantially uniform resistance from one insulator terminal to theother so as to eifect a substantially uniform resistance gradient of thevoltage drop over the insulator.

A further object of the invention is to provide an insulator which shallbe of improved construction and operation, particularly under adverseweather conditions.

Other objects and advantages will appear from I the followingdescription.

The invention is exemplified by, thelcombination and arrangement ofparts shown in the accompanying drawing and described in the followingspeciflcation, and it is more particularly pointed out in the appendedclaims.

In the drawing:

Fig. 1 is an elevation with part broken away showing a post insulatorhaving one form of the present invention applied thereto.

Fig. 2 is part elevation and part section of a suspension insulator,disclosing one embodiment of the'invention.

InFig. 1 the numeral ill designates an insulating member of porcelain orother suitable dielectric material having a base fitting l2 and a, boltl3 for securing the insulator upon a suit-- able support. A conductorgroove I4 and tie wire groove l5 or other suitable means is provided forsecuring a conductor at the topof the insulator. The insulator isprovided with a continuous helical flange l6 extending from the top tothe bottom of the insulator. The pitch of the outer periphery of theflange is such that water clinging to the outer edge of the flange willtravel very slowly in a circumferential direction and excessive waterwill drip from the edge of theflange rather than run down the helix.

For a glazed porcelain insulator, I have found that where the outerperiphery is 7% inches in diameter, a pitch of 1% inches will givesatisfactory results in this respect. This is a pitch of approximately1:20. The upper surface of the flange is considerably steeper than thecircumferential. pitch, an angle of about 22% degrees beingasatisfactory angle. The angle should be such that the water on the uppersurface of the flange will run readily to the outer periphery and excesswater will drip from ,the outer periphery but a sufllcient amount willcling to the lower edge to form a continuous conductor from the top tothe bottom of the insulator. It will be understood, of course, that theproportions and angles given above may be changed to suit varyingconditions, such as various atmospheric conditions and-differentmaterials, as well as the voltage to which the insulator is subjected;

Heretofore insulators have been designed to give as nearly a uniformdistribution of capacitance from one terminal to the other as possiblein order to give a uniform voltage gradient over the insulator. As longas the insulator is dry, the voltage gradient will be controlled chieflyby the distribution of capacitance as the leakage current will benegligible; but assoon as'the insulator becomes wet, the leakage currentwill begin to travel from one end-of the insulator. to the other and thevoltage drop in the leakage path, instead of the capacitancedistribution, will be the controlling factor in the voltage gradientover the insulator. I

I Insulators that have been desigined to give a satisfactoryvoltagegradient under dry conditions have been found to beveryunsatisfactory in this respect under wet conditions, due to theunequal distribution of the resistance in the wet leakage path. Usuallythe water will run olfrapidly from the upper part of a porcelaininsulator, producing a higher resistance over this part than over otherportions of the leakage path.-' Since the heat generated in a conductoris proportional to the resistance, the surface from which the water runsmost rapidly will also be, subjected to the greatest heateifect,furtherdrying the water from these portions of the insulator surfaceandconsequently further increasing the resistance .at these portions. Theresult is that the voltage will be concentrated over certain zones wheretheto the other and is regulated as to amount so as Y to be uniformthroughout its length, a substantially uniform leakage path is providedbetween the two terminals so that there are no high resistance portionsto produce excessive heat, tending to dry up the leakage path andconsequently no concentration of voltage over limited portions of theinsulator. The slow movement of the water from the top toward the bottomof the insulator will insure a continuous conductor as the water willmove on to any spot which might otherwise happen to be lacking in itssupply'of water. Since more water will strike on the upper flange thanon the lower ones, there will always be a suflicient supply of water atthe top of the insulator. The flange will be shaped so that theconductor ribbon extmds to the upper terminal as 'veil as the lowerterminal of the insulator. In some cases it may be desirable to coat asuflicient portion of the insulator at its top with metal to insureelectrical connection with the upper end of the conductor ribbon ofwater. The lower end may be coated in a similar manner but this isusually unnecessary because of the fact that the supply of water willrun over the lower end of the insulator and insure electrical connectionbetween the lower end of the flange and the lower fitting. The bottom ofthe flange also slopes toward its outer edge so that the conductingribbon will not tend to flow inwardly but will be concentrated at theouter edge of the flange.

Instead of depending upon a ribbon of water suspended from the outeredge of the flange by adhesion and surface tension, the flange may beprovided with a helical groove extending from one end of the insulatorto the other for retaining a suflicient amount of water to form aconductor path. Such a groove may be placed at various positions on theupper surface of the flange so as to intercept suilicient water to fillthe groove and the amount of water may be regulated by the depth andsize of the groove.

In the form of the invention shown in Fig. 2, a suspension insulatorhaving a central body portion I1 and flanges i8 is provided with agroove l9 at the base of the flange II and next adjacent the body 11.There is one advantage in placing the groove l9 adjacent the inner edgeof the flange because at this position the flange has a minimum radialdistance from the axis of the insulator and any tilting of the axis ofthe insulator away from vertical will produce the minimum amount ofvariation in the slope of the groove iii. If the groove is tilted toomuch, the water might not fill the groove uniformly as it will tend torun from the high side to the low side and thus interfere with theuniform resistance of the conductor path.

In order to enable the grading resistance to operate under fogconditions, as well as rain, there is shown in Fig. 2 a collector 20 atthe top of the insulator for condensing the fog from the atmosphere anddirecting it into the upper end of the groove is. This collector may bea metal screen secured to the upper fitting 2| in any suitable manner,as by means of a bracket 22. The fog will condense and collect on thescreen and run down into the upper end of the groove ii.

In practically all locations, atmospheric moisture, whether in the formof rain or fog, usually contains enough salts or other impurities insolution to form an electrolyte, rendering the water sufficientlyconductive to operate in the manner described above. If the moisture inthe atmosphere should ever chance to be of sufiicient purity as to benon-conducting and if there were not sufiicient impurities on theinsulator surface to render it conductive, then of course there wouldnot be sufficient current leakage over the insulator surface to destroythe capacitance gradient and consequently no need for resistancegrading. It will be understood of course that where, in thespecification and claims, water or moisture is mentioned, there is nointention to restrict the meaning to pure water but the expressionincludes atmospheric moisture containing sufilcient impurities to renderit conducting.

I claim:

1. The combination with an electrical insulator, of meansjor condensingmoisture from the atmosphere surrounding said insulator and fordirecting said moisture onto the surface of said insulator, saidinsulator having means thereon for retaining said moisture in asubstantially uniform conductor path from one terminal of said insulatorto the other.

2. In combination an insulator having a hellcal groove adapted to retainmoisture therein forming a conductor path from one terminal of saidinsulator to the other, and a moisture condensing device disposed at theupper end of said groove for directing moisture from the atmosphere intosaid groove.

3. An insulator having means for retaining moisture on the surfacethereof in a helical path from one extremity of said insulator to theother, and means spaced from the surface of said luaulator for directingmoisture from the surrounding atmosphere into said path.

4. An insulator comprising an elongated body having a helical flangethereon, terminals at opposite ends of said body, said flange beingarranged to slope outwardly and downwardly to cause water to runtherefrom and drip from the edge of said flange, said flange havingahelical groove in the upper surface thereof of less width than thetotal width of said flange to constrain a portion of the water disposedon said flange to follow said groove and form a leakage path ofsubstantially uniform resistance from one end of said insulator to theother.

5. An insulator comprising a dielectric body having terminals atopposite ends thereof and having a helical flange thereon, the uppersurface of said flange being inclined outwardly and downwardly to causewater to run from said flange radially of said insulator, the lowersurface of said flange also being inclined outwardly and downwardly toprovide a sheltered surface for maintaining dry surface resistance toleakage longitudinally of said insulator and means for constraining astream of water in a helical path on said flange of less width than thetotal width of said flange, the opposite ends of said path beingelectrically connected with the terminals at the opposite ends of saidinsulator.

6. An insulator comprising an elongated dielectric member havlng ahelical flange thereon, the pitch of said flange being such that waterthereon will travel very slowly in a circumferential direction andexcess water will drip from the edge thereof and not be thrown therefromby centrifugal force, said flange being constructed and arranged toretain a limited stream of water thereon to provide a leakage path ofsubstantially uniform resistance.

7. An insulator comprising an elongated dielectric body having a helicalflange thereon, the upper surface of said flange sloping outwardly anddownwardly to cause water to flow radially thereon and drip from theedge thereof, the radial pitch of said surface being greater than thehelical pitch of said flange so that water will flow by gravity from theedge of said flange, and means for constraining a deflnite amount ofwater to flow in a helical path on the surface of said flange from oneend of said insulator to the other to provide a leakage path ofsubstantially uniform resistance.

8. An insulator comprising a dielectric body, means for directing astream of water of definite cross section from the upper to the lowerportion of said dielectric body and a metal screen condenser forcollecting moisture and directing it into said stream at the upper endof said body.

JOHN J. TAYLOR.

